Simian virus 40 (SV40) is a small oncogenic mammalian virus. In order to understand its molecular biology more fully, I propose cloning and expressing certain sections of the SV40 genome in Escherichia coli and purifying the resulting polypeptides in order to either analyze their properties or raise antibodies which themselves would be used to probe SV40-infected mammalian cells. The regions of interest are: 1) The C-terminus of the large T gene, translated in an alternative reading frame (middle T); 2) The leader sequence of the late messenger RNA; 3) The central region of large T; 4) The C-terminus of small t; 5) The N-terminus of VP2. The purpose of producing specific antibodies is to distinguish between those SV40 specified proteins that cannot be resolved using present antibody preparations (t, T; and VP2, VP3), and to determine whether certain segments of the SV40 genome that could encode polypeptides actually do (middle T and the late leader sequence). The purpose of producing distinct sections of the T and t antigens is to investigate their biological role.